A set of APIs developed by Microsoft that enables programmers to write programs that access hardware features of a computer without knowing exactly what hardware will be installed on the machine where the program eventually runs. DirectX achieves this by creating an intermediate layer that translates generic hardware commands into specific commands for particular pieces of hardware. In particular, DirectX lets multimediaapplications take advantage of hardware acceleration features supported by graphics accelerators.

DirectX 2, released in 1996, supports the Direct3D architecture. DirectX 5, released in 1998, adds new layers to the DirectX API, In addition to the low-level layer that communicates directly with multimedia hardware, DirectX 5 also includes a Media layer that enables programmers to manipulate multimedia objects and streams. DirectX 5 also supports USB and IEEE 1394 buses, AGP, and MMX.